The present invention is related to thermoplastic elastomeric compositions particularly useful for tire and other industrial rubber applications, reinforced or otherwise, that require impermeability characteristics.
EP 0 722 850 B1 discloses a low-permeability thermoplastic elastomeric composition that is excellent as an innerliner in pneumatic tires. This composition comprises a low permeability thermoplastic in which is dispersed a low permeability rubber. EP 0 969 039 A1 discloses a similar composition and teaches that the small particle size rubber dispersed in the thermoplastic was important to achieve acceptable durability of the resulting composition.
There are also examples of the use of a thermoplastic elastomer composed of a rubber and a thermoplastic for use as an innerliner in a tire. But, in general, a flexible material of the type disclosed therein has low heat resistance. When the thermoplastic material in the composition has a melting point less than the tire vulcanization temperature, when the tire curing bladder is released at the end of the curing cycle, the inside surface of the tire may have defects due to the thermoplastic material of the composition sticking to rubber of the curing bladder.
Controlling the viscosity difference between the two different materials in the composition is also considered important, as the viscosity difference affects the dispersed rubber particle size. However, when seeking to maintain a ratio of melt viscosities of the rubber/plastic at 1.0 (one), the rubber may dominate the matrix and the composition no longer exhibits a desired thermoplasticity, see EP 0 969 039 A1.